12: The predictive capacity of Uterine artery Doppler for preterm birth - a prospective cohort study

Abstract

Mid-trimester Uterine Artery (UtA) resistance measured with Doppler sonography is known to be predictive for preeclampsia and thus iatrogenic preterm birth (iPTB). In view of the emerging association between hypertensive disease in pregnancy and spontaneous preterm birth (sPTB), we hypothesized that UtA resistance could predict sPTB. We performed a prospective cohort study. During the 18-22 week routine fetal anomaly scan we measured UtA resistance in singleton pregnancies. Pregnancies complicated by major congenital anomalies were excluded. We classified the resistance in the uterine artery (no notch, unilateral notch or bilateral notch) and related it to sPTB and iPTB, defined as delivery before 37 weeks, using likelihood ratios. Furthermore, we assessed whether the UtA Pulsatility Index (PI) was associated with the risk of sPTB. Between January 2009 and December 2016, we included 2,987 women. Mean gestational age at measurement was 19+6 weeks. There were 79 (2.6%) women with a bilateral notch and 134 (4.5%) with a unilateral notch. Mean gestational age at birth was 39+0 weeks, 6.3 % had sPTB while 4.0 % had iPTB. Mean UtA resistance was 1.11 in the sPTB group compared to 1.05 in the term group (p <0.001). The risk of PTB was increased with high UtA resistance (OR 2.6 per unit ; 95% CI 2.0-3.4). Figure 1 shows the time to delivery. The prevalence of spontaneous preterm birth increased from 6.1% in women with normal uterine arteries to 9.0% in women with a unilateral notch and 10.1% in women with a bilateral notch (Table 1). For iPTB, these rates were 3.4%, 9.0% and 19.0% respectively. Likelihood ratios for the prediction of sPTB were 1.5 (95% CI 0.8-2.7) and 1.7 (95% CI 0.8-3.6) for unilateral and bilateral notches respectively, and 2.6 (95% CI 1.4-4.6) and 6.0 (95% CI 3.3-10.3) for iPTB. Of all women with bilateral notching 29.1% delivered preterm. Mid-Trimester UtA resistance measured at 19 weeks gestation predicts sPTB.View Large Image Figure ViewerDownload Hi-res image Download (PPT)